Catalogo Articoli (Spogli Riviste)

OPAC HELP

Titolo:
Catalytic study of methanol-to-olefins conversion in four small-pore silicoaluminophosphate molecular sieves: Influence of the structural type, nickel incorporation, nickel location, and nickel concentration
Autore:
Djieugoue, MA; Prakash, AM; Kevan, L;
Indirizzi:
Univ Houston, Dept Chem, Houston, TX 77204 USA Univ Houston Houston TX USA 77204 uston, Dept Chem, Houston, TX 77204 USA
Titolo Testata:
JOURNAL OF PHYSICAL CHEMISTRY B
fascicolo: 27, volume: 104, anno: 2000,
pagine: 6452 - 6461
SICI:
1520-6106(20000713)104:27<6452:CSOMCI>2.0.ZU;2-D
Fonte:
ISI
Lingua:
ENG
Soggetto:
ELECTRON-SPIN-RESONANCE; ADSORBATE INTERACTIONS; SILICON INCORPORATION; ECHO MODULATION; SAPO ZEOLITES; LIGHT OLEFINS; HYDROCARBONS; ACIDITY; ETHENE; SELECTIVITY;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
42
Recensione:
Indirizzi per estratti:
Indirizzo: Kevan, L Univ Houston, Dept Chem, Univ Pk, Houston, TX 77204 USA Univ Houston Univ Pk Houston TX USA 77204 , Houston, TX 77204 USA
Citazione:
M.A. Djieugoue et al., "Catalytic study of methanol-to-olefins conversion in four small-pore silicoaluminophosphate molecular sieves: Influence of the structural type, nickel incorporation, nickel location, and nickel concentration", J PHYS CH B, 104(27), 2000, pp. 6452-6461

Abstract

The selectivity of four small-pore silicoaluminophosphate molecular sieves, including SAPO-34 (CHA), SAPO-35 (LEV), SAPO-17 (ERI), and SAPO-18 (AEI),toward light olefins in general and ethylene in particular has been investigated for the methanol-to-olefins reaction using gas chromatography. This study was prompted by earlier electron spin resonance and electron spin-echo modulation results on nickel-modified SAPO materials in which NI(I) was incorporated into both framework and ion-exchanged sites. These seemingly similar materials behaved significantly differently with respect to reducing agents and adsorbates. Attention was focused on whether the catalyst performance is influenced by the structural type, the presence of a transition metal ion (Ni) either in the framework or at ion-exchanged positions, or the amount of incorporated transition metal ion. Our results show that these factors indeed play an important role in the catalytic behavior. Among the protonated H-SAPO-n materials, the highest combined distribution of ethylene,propylene, and butenes (C-2-C-4 olefins) was obtained with H-SAPO-34, and the lowest with H-SAPO-35, which also had the shortest lifetime for catalytic activity. H-SAPO-18 turned out to be the best catalyst in terms of lifetime for catalytic activity. Incorporation of N(II) into the framework increased the lifetime, the overall distribution of C-2-C-4 olefins tin the caseof NiAPSO-34), and the selectivity of the catalysts toward ethylene (in the cases of NiAPSO-34 and NiAPSO-18), whereas incorporation of Ni(II) by means of solid-state ion exchange (NiH-SAPO-n) increased only the selectivity toward ethylene. Also, the increase in ethylene selectivity was more prominent in synthesized than in ion-exchanged samples. Among the Ni-loaded samples, NiAPSO-34 was found to be the best catalyst in terms of both ethylene selectivity and lifetime, whereas NiH-SAPO-18 exhibited the worst ethylene yield and NiH-SAPO-35 the shortest lifetime. Finally, the effect of the amount of Ni was investigated in NiAPSO-34. It appears that the selectivity toward ethylene does not increase linearly with NiAPSO samples prepared with an increasing amount of Ni in the reaction gel. In fact, there seems to be an optimum Ni concentration for which ethylene selectivity reaches a maximumand above which ethylene selectivity decreases. This optimum concentrationis the same as was found in earlier studies to yield the strongest Ni(I) signal, as observed by ESR.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 13/07/20 alle ore 09:52:08